In a typical communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or user equipments (UE), communicate via a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, with each service area or cell area being served by a radio access network (RAN) node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” or “eNodeB”. The area or cell area is a geographical area where radio coverage is provided by the radio access network node. The radio access network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio access network node. The radio access network node communicates over a downlink (DL) to the wireless device and the wireless device communicates over an uplink (UL) to the radio access network node.
A Universal Mobile Telecommunications System (UMTS) is a third generation telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the 3rd Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several radio access network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural radio access network nodes connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a 3GPP radio access technology wherein the radio access network nodes are directly connected to the EPC core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio access network nodes connected directly to one or more core networks.
In LTE, a wireless device may encounter a radio link failure (RLF). The criteria for RLF is based on that the wireless device starts a timer when it detects radio link problems. If the radio link problems stop the timer resets, but if the timer times out before the radio link problems have stopped the wireless device will initiate a radio link failure procedure. When this happens, the wireless device performs a cell re-selection and re-establishes the connection towards the network. The most likely scenario is that the wireless device selects and camps in a different cell than from the one the wireless device was connected to when the wireless device experienced the RLF.
When the wireless device performs the re-establishment of the connection, the wireless device will first try to re-establish a Radio Resource Control (RRC) connection with the RAN. If this fails e.g. due to that the radio access network node does not have access to a RRC context for the wireless device, the wireless device will start a new RRC connection and send a Non Access Stratum (NAS) service request message, in order to be able to re-establish the connection based on CN/NAS layer information.
During this process, the radio access network node, to which the wireless device was connected when the wireless device experienced the RLF, may be buffering the wireless device DL data. If the wireless device succeeds with the re-establishment of the connection, the wireless device will typically be able to recover any packets stored in the radio access network node serving the cell the wireless device was previously served in but if the wireless device fails to re-establish the RRC connection it is today not possible to recover any packets since the wireless device will initiate another RRC connection and the context will be re-built from the CN context. During this procedure the CN will release an old S1 connection to the radio access network node where any packets are stored and these will be lost. All the data buffered in the radio access network node may thus be lost and not re-directed to a new radio access network node in which the wireless device tries to connect after a RLF event or in other situations when the wireless device moves to a different radio access network node. Transport layer or application layers may recover the packets; however, that implies a considerable delay. This results in a limited or poor performance of the communication network.